RFR: 8296970: Remove sysThreadAvailableStackWithSlack from hotspot-symbols

[Man Cao]

Hi all,

Could anyone review this cleanup to remove dead symbol "sysThreadAvailableStackWithSlack"? See https://bugs.openjdk.org/browse/JDK-8296970 for more details.

-Man

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Commit messages:
 - 8296970: Remove sysThreadAvailableStackWithSlack from hotspot-symbols

Changes: https://git.openjdk.org/jdk/pull/11156/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11156&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296970
  Stats: 4 lines in 2 files changed: 0 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/11156.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11156/head:pull/11156

PR: https://git.openjdk.org/jdk/pull/11156